The present invention generally relates to signal pickup devices in rotary recording medium reproducing apparatuses, and more particularly to a signal pickup device in which a cantilever having a reproducing element at the tip end thereof is supported by a resilient support member, so that the cantilever is at a position where the cantilever does not project from the signal pickup device when the signal pickup device is not in use.
Apparatuses have been reduced to practical use, which is capable of reproducing a recorded information signal from a rotary recording medium (hereinafter simply referred to as a disc) in which an information signal such as a video signal and an audio signal is recorded as variations in geometrical configuration, according to variations in electrostatic capacitance between the above disc and an electrode of a reproducing stylus. In a signal pickup device used in a reproducing apparatus of the above type, the reproducing stylus is receded inside the signal pickup device when the signal pickup device is not in use, in order to protect the reproducing stylus. When the signal pickup device is in use, the signal pickup device is constructed to lower the reproducing stylus, so that the reproducing stylus makes contact with and can slide against the surface of the disc.
Accordingly, the present inventor has previously attempted to realize a signal pickup device in which a part in the vicinity of the rear end of a cantilever having a reproducing stylus at the tip end thereof, is supported by a resilient support member. Hence, in this signal pickup device, the reproducing stylus is receded inside the signal pickup device when the signal pickup device is not in use, and the reproducing stylus is forcibly lowered when the signal pickup device is in use. However, in this signal pickup device, the mounting angle is difficult to determine when the above resilient support member is mounted to a frame of a pickup cartridge which forms an essential part of the signal pickup device. Therefore, inconsistency is introduced in mounting the above resilient support member to the frame of the pickup cartridge. When inconsistency is introduced upon mounting of the resilient member onto the main body of the signal pickup device, there are cases where the reproducing stylus is not completely receded inside the signal pickup device when the signal pickup device is not in use. Further, the height position of the reproducing stylus with respect to the disc becomes inconsistent. Hence, there was a disadvantage in that the stylus pressure of the reproducing stylus with respect to the disc became inconsistent, even when the reproducing stylus is lowered by a constant force.
Moreover, in an apparatus which reproduces a disc in which the above information signal is recorded in a main track without forming a guide groove for the reproducing stylus, and reference signals for tracking control are recorded on both sides of the main track, the cantilever is displaced by obtaining a tracking control signal from the reproduced reference signals. In this reproducing apparatus, tracking control is performed so that the reproducing stylus accurately traces over the main track. In addition, the cantilever is displaced in the longitudinal direction thereof according to a jitter compensation signal, in order to perform jitter compensation.
The resilient support member which supports the above cantilever is repetitively deformed in response to the movement of the cantilever, when the cantilever swings or moves in the longitudinal direction thereof within a minute range, due to the tracking control operation, jitter compensation operation, wobble in the surface of the disc, and the like. The frequency characteristic of the signal pickup device is determined by the distance of the range in which the resilient support member undergoes resilient deformation.
Conventionally, the resilient support member is mounted onto the frame of the pickup cartridge by inserting the tip end sides of arms of the resilient support member into the cutout of the frame, to fix the inserted part by a binding agent. Accordingly, depending on whether the binding agent is adhered to the outer side or the inner side of the frame of the pickup cartridge, the length of a part of the resilient support member which undergoes resilient deformation differs. Therefore, there was a disadvantage in that the frequency characteristic of the assembled signal pickup device was inconsistent due to the above described reasons.